Structure for gunpowder charge in multi-frac composite perforating devices

Abstract

This invention provides a structure for gunpowder charge in multi-frac composite perforation devices that is easy to assemble and transport while the charge volume of gunpowder is increased. In one embodiment of the present invention, an triplet outer gunpowder box is attached onto the outer wall of the charge frame and comprises one middle gunpowder box charged with gunpowder of certain burning rate, and two side-hung gunpowder boxes charged with gunpowder of another burning rate. The two side-hung gunpowder boxes are separately located on the two sides of the middle gunpowder box and are connected with the middle gunpowder box as a unit. The middle gunpowder box is located at a position corresponding to the perforating charge, and has an inner groove for orienting the perforating charge and a through hole through which the jet flow passes.

What is claimed is: 
     
       1. A structure for gunpowder charge for a multi-frac composite perforation device that comprises an inner gunpowder box between adjacent perforating charges in the charge frame  1  of said perforation device, said structure for gunpowder charge comprises a outer gunpowder box  4  attached to the outer wall of the charge frame  1 , wherein said outer gunpowder box  4  comprises a middle gunpowder box  3  and two side-hung gunpowder boxes  2 A and  2 B, wherein said boxes  2 A and  2 B are separately located on the two sides of said middle gunpowder box  3 , and wherein the gunpowders charged in said inner gunpowder box and outer gunpowder box  4  are classified into three types: high burning rate gunpowder having combustion endpoint of 25˜80 ms, middle burning rate gunpowder having combustion endpoint of 80˜280 ms and low burning rate gunpowder having combustion endpoint of 300˜800 ms. 
     
     
       2. The structure for gunpowder charge of  claim 1 , wherein the time difference between the pressure peaks of the middle burning rate gunpowder and the high burning rate gunpowder is 5˜10 ms, and the time difference between the pressure peaks of the low burning rate gunpowder and the middle burning rate gunpowder is 20˜50 ms. 
     
     
       3. The structure for gunpowder charge of  claim 1 , wherein the middle gunpowder box  3  and the two side-hung gunpowder boxes  2 A and  2 B are connected by a hinging mechanism, strapping with flexible belt or bonding with adhesive. 
     
     
       4. The structure for gunpowder charge of  claim 1 , wherein said middle gunpowder box  3  is located at a position corresponding to the open jet emitting end of a perforating charge. 
     
     
       5. The structure for gunpowder charge of  claim 1 , wherein the inner side of said middle gunpowder box  3  has an inner groove  32  for orienting the perforating charge and a through hole  33  through which the jet flow passes. 
     
     
       6. The structure for gunpowder charge of  claim 1 , wherein gunpowder P charged in said middle gunpowder box  3  is high burning rate gunpowder, gunpowder Q charged in said inner gunpowder box between adjacent perforating charges inside the charge frame is low burning rate gunpowder, and gunpowders R 1  and R 2  charged in the side-hung gunpowder boxes  2 A and  2 B are middle burning rate gunpowders. 
     
     
       7. The structure for gunpowder charge of  claim 6 , wherein the burning rates of gunpowders R 1  and R 2  are the same or not the same. 
     
     
       8. The structure for gunpowder charge of  claim 1 , wherein the side-hung gunpowder box  2 A or  2 B contains proppant. 
     
     
       9. The structure for gunpowder charge of  claim 1 , wherein the outer gunpowder box  4  is attached to the outer wall of the charge frame  1  by means of:
 clamping, wherein the inner side of the side-hung gunpowder boxes  2 A and  2 B has claws  22  and  23  for fitting into the installation holes of charge frame  1  or inserting into the grooves of charge frame  1 ; or, 
 spring jig, wherein gunpowder box  4  is attached to the outer wall of the charge frame  1  by a matching structure of a lock hook  24  and a lock catch  25 .